1. Technical Field of the Invention
The present invention relates to a radio frequency circuit module, such as monolithic radio frequency integrated circuit module or a hybrid microwave integrated circuit module, formed by mounting circuit elements on a circuit substrate having dielectric layers for a module and a communication apparatus using the radio frequency circuit.
2. Description of the Prior Art
Heretofore, there is a radio frequency integrated circuit module having a multi-layer circuit substrate, on which circuit elements such as active elements including transistors and diodes and passive elements including resistors and inductors, and wiring for mutually connecting the circuit elements are mounted. When radio frequency integrated circuit module are mutually connected, a transmission path having a high shield property, such as a coaxial line, is used between transmission and reception terminals in many cases.
FIG. 16A is an oblique view conceptually showing the vicinities of transmission and reception terminals of a conventional radio frequency integrated circuit module. FIG. 16B is a sectional view of FIG. 16A in a coaxial line direction. FIG. 16B shows a radio frequency integrated circuit module having a multi-layer circuit substrate 2001 formed by interposing an inner conductor 2002 having circuit elements mounted thereon, between first and second grounds 2003 and 2004 to form a strip line 2005.
The inner conductor 2002 is led to a pad 2007 through a via (through hole) 2006. The pad 2007 is a transmission and reception terminal having a fixed area provided on a top layer or a bottom layer. A central conductor 2009 of a coaxial line 2008 is fixed to the pad 2007 by adhering using solder 2010. Furthermore, the first and second grounds 2003 and 2004 are electrically connected through vias 2011. An outer conductor 2012 of the coaxial line 2008 is adhered and fixed to the first ground 2003 by solder 2013.
Radio frequency signals can be inputted to and outputted from the radio frequency integrated circuit module of such construction in such a state that circuit elements are integrated therein.
In the conventional radio frequency integrated circuit module, however, the central conductor of the coaxial line to be shielded around it is exposed at a portion connected to the pad. Therefore, the central conductor is susceptible to electromagnetic waves radiated from circuit elements and wiring mounted near the central conductor or external electromagnetic noise.
Furthermore, in some cases, for example, the central conductor of the coaxial line is pulled from the outside and consequently a warp is caused in the multi-layer circuit substrate, or stress from a contained cabinet is applied to the coaxial line. Sometimes in this case, solder peels from the pad or ground, or a metal pattern peels from the multi-layer circuit substrate, and resultant wire breaking or poor connection degrades the electric connection state.
Furthermore, there is a disadvantage that an unnecessary inductance component increases because the via is provided to connect the inner conductor, and consequently the radio frequency characteristics are degraded. Furthermore, since the central conductor of the axial line is not connected to the inner conductor in a three-dimensional rectilinear way, the electromagnetic field near the via is disturbed and the transmission characteristics of the radio frequency signal are degraded in some cases.